PROGNOSTIC FACTORS IN PATIENTS WITH RECTAL CANCER TREATED WITH ADJUVANT RADIOTHERAPY

Sixty-two patients with locally advanced rectal cancer received adjuvant radiotherapy in Dokuz Eylül University Radiation Oncology Department between August 1991 and May 1997. Of these 62 patients, 55 were taken into evaluation with respect to prognostic factors, retrospectively. There were 35 (64%) male and 20 (36%) female patients. Median age was 53 years (range: 19-73). Twenty-two cases (40%) had tumors lower than 5 cm from the anal verge while 33 cases (60%) had tumors located more proximally. The distribution of patients according to the type of surgery was as follows: abdominoperineal resection, 20 patients (36%); low anterior resection, 18 patients (33%), and anterior resection, 17 patients (31%). Thirty-one patients (56%) were operated at Dokuz Eylül University and 24 (44%) were operated at other centers. According to the Modified Astler-Coller Staging system pathological stages were: B1, 5 cases (9%); B2, 26 cases (47%); B3, 4 cases (7%); C1, 1 case (2%); C2, 13 cases (24%) and 03, 6 cases (11 %). All of the B1 cases had preoperative radiotherapy. Radiotherapy was given in daily fractions of 180 or 200 cGy in all patients except the two (one patient received 15x230 cGy, and the other received 1x500 cGy preoperatively), and the mean dose of the postoperative radiotherapy alone was 46.6 Gy (BED3 3Gy= 76.4 Gy), and the mean dose of the postoperative radiotherapy alone was 52.1 Gy (BED3 3Gy= 83.8 Gy). Concomittant chemotherapy was applied to 24 cases (44%) (350 mg/m2 5FU+20 mg/m2 leucovorin IV bolus on the first and last three fractions or radiotherapy). Overall survival rate calculated with Kaplan-Meier method at 2 and 3 years was 75.3% and 55.6% respectively. Age, type of surgery, institution of surgical operation, tumor location, pathological stage, lymph node involvement, use of concomitant chemotherapy were the prognostic factors analyzed. Among these prognostic factors, only the lymph node involvement (P=0.00588) and the pathological stage (P=0.00288) were found to be significant in the univariate analysis performed by chi-square test. In the univariate Cox regression analysis, lymph node involvement (RR:4.7; 95% Cl; 1.9-11.6) and pathological stage (RR:5.2; 95% Cl: 2-13.6) appeared as significant prognostic factors. In the multivariate Cox regression analysis, none of the factor analyzed reached statistical significance. Since the close relationship between lymph node involvement and pathological stage seemed to cause this result, multivariate analysis was performed excluding lymph node involvement, then pathological stage emerged as a significant prognostic factor (RR:5.8; 95% Cl:2-16.5). When the multivariate analysis was repeated excluding pathological stage, then lymph node involvement gained prognostic significance (RR:5.3; 95% 01:1.9-14.7).